Jerry,
Several things come to mind:
1. The coax link between the transceiver and 87A should be about 6 feet
long, and definitely not less than that. ETO provided a 6' coax link with
the amp, which you probably didn't get with your used unit. My experience
has been that a shorter link results in somewhat high input SWR. Lengths
longer than 6' will probably work, but there are some lengths that will give
you higher SWR than others. Try links of various lengths and see what you
get.
2. The figures you listed aren't all that bad. The amp input SWR typically
won't be 1.0:1. It's certainly not unusual for it to be, say, 1.5:1 or even
a little higher in some parts of the band. However, it should be under 2.0:1
everywhere. As long it's under 2.0:1 and your transceiver puts out enough
power to drive the amp, I wouldn't worry about it.
3. The input bandswitch may be dirty. It's accessible through a small door
on the bottom of the amp. You could try some good quality contact cleaner on
it. It's also possible the bandswitch is bad. Mine eventually went bad, but
only on one band (10m).
4. I would not attempt to adjust the input coils. You're likely to make
things worse. But you might try to find out if the previous owner(s) tried
to do this. That might explain some of the high SWR figures.
5. The band switch may be out of calibration. The band switch is calibrated
at the factory so that it lands with the contacts fully engaged. Each amp's
calibration factors are patched into its firmware. Aging can cause the band
switch to get out of calibration. Sometimes bumping the factors a little in
one direction or the other will seat the contacts better and will improve
the input SWR. The factory should be able to help you determine whether this
is the case.
Hope this helps.
73, Dick WC1M
> -----Original Message-----
> From: JOS Earthlink [mailto:jsternmd@earthlink.net]
> Sent: Sunday, December 31, 2006 4:35 PM
> To: amps@contesting.com
> Subject: [Amps] Alpha 87a
>
> Hi All,
>
> I just got an ETO Alpha 87a with Alphamax and it seems to
> work very nicely.
> I only see one problem with the amp - I'm almost certain that
> the RF input coils for many of the bands need to be
> adjusted. I noticed that the SWR out of the TS-950SD was
> running high into the 87a on a few bands. To be absolutely
> certain I placed my Powermaster powermeter between the
> TS-950SD and the 87a. I think the 87a RF input circuits are
> out of whack:
>
> At 28.0000 - 29.7000 Mhz SWR into the 87a is from 1.5 - 2.0
> At 21.0000 - 21.4500 Mhz SW goes from 2.3 - 1.8 At 18.068 -
> 18.168 Mhz SWR goes from 1.7 - 1.4 At 3.5000 - 4.000 Mhz SWR
> starts at 1.3 but goes 2.2 above 3.700 Mhz.
>
> I tried this with other tranceivers instead of the TS-950SD
> and all show the same. On my Collins 30L-1 it's a piece of
> cake to adjust the RF coil for each band by looking at
> Reflected power between the exciter and amp tuning the RF
> coil for minimal Reflected power but the 87a is a new beast
> for me plus I don't have any schematics. Any advice appreciated.
>
> Have a Happy and Healthy New year to All !
>
> 73 Jerry
> K1JOS
> CCA #11906
>
>
>
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